Electrostatic detearing apparatus



June 1953 H. K. STODDARD ELECTROSTATIC DETEARING APPARATUS Filed 001;. 22, 1945 v IN VEN TOR. HAROLD A. 5700014190 Patented June 2, 1953 ELECTROSTATIC DETEABING Harold K. Stoddard, Indiana olis, 1nd,, ase snor, by mesne assignmen to Hamburg E ectra ating Co n-l Indianapolis, 1nd,, a c rporation of Indiana Appli n e -'22, %5, Seri l No. 62338.1

whims, (Cl-1 8mm) This invention relates to an apparatus forlec trostaticallv detectingarticles to which an ex .cess of liquid coating material has been applied, and more particularly to an electrostatic deteare 'ing apparatus suitable for use when they liquid coating material possesses relatively high elec trical resistance.

United States Letters Patent No. 2,359,476. to Gravley, discloses an apparatus and a method for effecting the electrostatic detear-ing of excess liquid coating material applied to an article. In

the practice of the Gravley method, the. article to be coated is first treated, as by dipping, with an excess of coating material and is thenbrought into spaced relation with a ot-carin electrode between. which and the articl a su antial elec t-rical potential difference is maintained. The

electrostatic field resulting from such potential difference promote the removal of excess coat.-

ir g material irom the article.

inmost commercial applications of the (Tr-ratios invention, the articles being coated are suspend,- ed from an overhead conveyor, moved through a bath of coating material, and then past the detearing electrode before such coating material has set. In the Gravley patent and in all com.-

mercial in tallations of which I am aware, the detearlng electrode is a flat; sheet of greater exnt han that of theert e es b i deteared and is positioned to Pr s nt its broad surface toward such articles.

Ihave discovered that whent e liquid coatin mater al applied. to the articles is a relatively poor conductor of ele tricity t e e ss o ng material which flows downwardly over the sur iaee of the-article toward th p t f det ctingand which would normally be deteared by the action of the field is, "in some instances, repelled upwardly from the lowermost point or points of the article to form a ridge or head on other por tions thereof "and is not deteared. In some cases, this repulsion is so strongthat the "bottom edge of the article-will be substantially lea-red. i have also discovered that inthecase of an article coat.- ed on both the inside and outside it issometimes v d ifdcult to secure satisfactory detearing of both article o' e d tected to an electros atic :flieldore ated with the aid or a detearin oleotrodewh 13 presents toward the article or articles, being teared one or more detearing' surfaces having at least one dimension which is relatively small. When the article or articles .to be .deteared are hollow and supported with open ends directed toward the electrode, each detearing surf ,9: preferably has one dimension not materially greater than he diameter of the open endoieach article. If the articles to bedetea-redlare moved cont nuous y pa t t electrode, the detectin surfa e may e a narr w sur aeeextendin arallel to the direction .01? article moveiner-it. Who 9 art cles to be d cted ar m ved past the el trade whil a anged in rows or roups e vs ing transversely of the path-01E movement, 1 ll elec rode ma emitters-pl a oflaterallr d, a cont n ous. longitudinally extending, relatively detect ng rfa s- T accompan g drawing llust at s my invention; Fig. 1 is an isometric view, somewhat diagrammatic in character, illustrating ,oneiorni of apparatus suitable to! use in employin 'lmy invention; and Fig. 2 is a ilt agmental end eilevation of the apparatus illustrated in Big. I Y

The apparatus illustrated in Fig. 1 .enibotl fi conveyor ID from which the articles H to be coated are suspended through hangers l 2 fe'lec's :tricai y QQ ducting' al T e conve or l is ar anged to move the art cles h ou h e means. (not shown) by h h n e cess of to. its mate ial is appl ed, and then o e some spaced re at on to a det ting electr de seas..- nated it enti t by t f renc numeral it, *The d tectin -electrode, as s o is sup' ported from o erh ad throu h insulators J4 and connected by "a conductor 15 with one tenininal of a high-voltage source l6' the other terminal or which is grounded as indicated at ously indicated, when the date no e a flat sheet and when the coat ng he applied to the cartridge cases is, like cy lopentadiene for x pl a rela ively po r c nduetor of electricity, the dctea-ring .olf eiifififis c at n ater al m-thecas s presents considerable dimculty. In some instances, the'coatihg I 3 material, instead of flowing downwardly over the outer surface of the cases to be deteared therefrom by the action of the field, seems to be repelled from the lower ends of the cases before it reaches such lower ends; and, as a result, the coating material may tend to form an annular ridge around the cartridge case a short distance above the lower end thereof.

Even when the coating material is a relatively good conductor difiiculty is frequently encoun-.

tered in securing satisfactory detearing of 1101-,- low articles; for adequate detearing of exterior detearing of interior surfaces may involve the articles to be deteared, means including a highvoltage source for maintaining an electrostatic field between said electrode and each group of articles moving past it, said electrode comprising a plurality of elements on one side of said groups extending generally parallel to the path of article movement and spaced laterally from each other and presenting relatively narrow surfaces toward the articles.

2. In electrostatic detearing apparatus, a detearing electrode, means for moving articles to I v be deteared past said electrode and in spaced resurfaces is usually accompanied by inadequate-g: detearing of interior surfaces, while adequate removal of too much coating material from exterior surfaces.

I have found that the difiicu lti es just referred I to can be eliminated by proper construction of the electrode l3. One suitable electrode, that shown'in'the drawing, embodies a pair of longitudinally extending rods it supported in later'allyspaced relation on cross-members ll attached to the insulators l4. Desirably the rods l6 have a diameter not materially greater than that of the open end of each of the articles II to be deteared. The rods Hi are arranged laterally of the path of conveyor movement so as to be within the lateral limits of the group of articles'suspended from each hanger l2 and preferably so as to be symmetrically arranged relative to such group of articles.

- "The number and spacing of the rods it may be varied depending upon the number and spacing of the articles If as well as upon the distance between the electrode and articles and the potential difierence maintained. For example the modification shown contemplates a potential difference of the order of 80,000 to 100,000 volts, an electrode-article spacing of about 8 inches, an interval of about 1%. inches between articles, and a spacing between the rods N3 of 4 to 5 inches.

The electrode illustrated and just described produces "improved results in the detearing of hollow articles supported with their open ends directed toward the electrode, especially if the coating material applied to such articles is a relatively poor electrical conductor. Because of the limited extent of the cross-members l1 longitudinally of the path of article travel and also because those cross members are at a greater distance from the articles than are the rods IE, the character of the electrostatic field and its effectiveness in producing satisfactory detearing are almost entirely dependent upon the width and spacing of the detearing surfaces which the rods present toward the articles. While the rods 16 are shown as round, with the result that the detearing surfaces are relatively sharply curved, this is immaterial to my purpose, and

rods of other'cross-sectional shapes may be emlation thereto, said means comprising a conveyor and a plurality of hangers each adapted to support in a group extending transversely of the path of conveyor movement a plurality of articles to be, deteared, means including a highvoltage source for maintaining an electrostatic field between said electrode and each group of articles moving past it, said electrode comprisinga plurality of relatively narrow elements on one .sideof said groups extending generally parallel to the path of article movement and spaced laterally from each other, the outermost of said elements lying within the projected lateral limits of each group of articles. p

3. In electrostatic detearing apparatus, a detearing electrode, means for moving articles to be deteared past said electrode and in spaced re- :lation thereto, said means comprising a conveyor and a plurality of hangers each adapted to support in a group extending transversely ofthc path of conveyor movement a plurality of articles to be deteared, means including a highvoltage source for maintaining an electrostatic field between said electrode and each group of articles moving past it, said electrode presenting toward the articles a pluralityof detearing surfaces which are discontinuous laterally with respect to the direction of article travel and'which are located on one side of such path, the outermost of said surfaces lying within the projected lateral limits of the group of articles.

4. In electrostatic detearing apparatus, a detearing electrode, means for moving articles to be deteared past said electrode and spaced relation thereto, said means comprising a conveyor and a plurality of hangers each adapted to support in a group extending transversely of the path of conveyor movement a plurality of articles to be deteared, means including a highvoltage source for maintaining an electrostatic field between said electrode'and'each group of articles moving past it, said electrode presentingtoward the articles a plurality of detearing surfaces which are discontinuous laterally with respect to the direct of article travel and which are located on one side of said groups. v 5. In electrostatic detearing apparatus, a detearing electrode, means for moving articles to be deteared past said electrode and in spaced relation thereto, means including a high-voltage source for maintaining an electrostatic field between said electrode and articles moving past it, said electrode comprising a plurality of elements on one side of said articles extending generally parallel to the path of article movement and spaced laterally from each other and presenting relatively narrow surfaces toward the articles. 6. In electrostatic detearing apparatus, a detearing electrode, means for moving articles to be deteared past said electrode and in spacedrelation thereto means including source for maintaining an electrostatic field between said electrode andarticlesmoving past it,

a high -voltage said surfaces lying within the projected lateral" limits of the group of articles.

7. In apparatus for detearing an article having an open end and interior and exterior surfaces to he deteared, a support for the article, an electrodelocated opposite the open end of an article on said support and spaced therefrom, said electrode presenting toward said article a detearing surface having one dimension not materially greater than the distance across the open end of the article, and means for maintaining an electrostatic field between said electrode and an article on said support.

8. In apparatus for detearing an article having an open end and interior and exterior surfaces to be deteared, an electrode having an elongated detearing surface the width of which is not materially greater than the distance across said open end, a conveyor for moving the article longitudinally of and in spaced relation to said detearing surface with its open end presented theretoward, and means for maintaining an electrostatic field between said electrode and an article moving past it.

HAROLD K. STODDARD.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,354,930 Williams Oct. 5, 1920 2,152,077 Meston et a1 Mar. 28, 1939 2,247,963 Ransburg et al July 1, 1941 2,269,592 McGraw Jan. 13, 1942 2,359,476 Gravley Oct. 3, 1944 

